DESCRIPTION: (Applicant's Abstract) This proposal is in direct response to a call for investigations of "selective cognitive deficits" rising from "neurodevelopmental disorders," and the application of such finding to the understanding of fundamental brain-behavior relationships. Our studies of infantile autism suggest a new and unexpected role for the cerebellum in cognition: rapid orientation and re-orientation of attention. We propose to investigate whether this reflects a general relationship rather than one that is unique to this developmental disorder, and to determine whether systems with which the cerebellum is interconnected (such as frontal and parietal cortex) perform comparable or complementary attentional operations. Hypothesis to be tested in this proposal are: a) the cerebellum is of critical importance for the rapid orientation or re-orientation of an attentional focus; b) parietal cortex is primarily involved in attentional operations outside the central attentional focus (e.g., monitoring information at locations of potential future importance); and c) frontal cortex is primarily involved in attentional operations within an attentional focus (including selection and maintenance of that focus). To test these hypotheses we will study adult patients (age 18-70) with cerebellar, parietal or frontal damage due to stroke, as well as age and gender matched normal controls. Behavior and event-related potentials will be recorded during two different but complementary sets of visual- spatial attention experiments that index the attentional operations of interest. Since we will be testing patients with damage to the cerebellum and frontal lobes, our measures are designed to be independent of motor response. MR imaging will be used to verify and quantify site and size of lesion as well as residual cortical and subcortical parenchyma. ERP and behavioral measures will be correlated with site and size of lesion, a procedure that has been successfully employ in comparable experiments. The experiments proposed here are designed to elicit double dissociations of anatomic damage and impaired concept that the cerebellum plays a specific role in the dynamic control of attentional resources, and will expand our knowledge of the complementary roles of subcortical and cortical systems in human attention.